As a penetration rate of automobiles increases and communication and multimedia technologies develop rapidly, a head unit, i.e., Audio Video Navigation (AVN) which may integrally use MP3, video, DMB, navigation, telematics and the like as well as existing AM/FM radio is recently installed in a vehicle.
In order to receive these services through the AVN in the vehicle, a roof antenna which is a unified antenna for wireless communication should be installed on a roof panel of the vehicle. The roof antenna may be roughly classified into a shark fin shape and a micro pole shape according to an external appearance thereof.
Also, as illustrated in FIG. 1, the roof antenna can be divided into a transmitter/receiver module separation type as shown in FIG. 1A and a transmitter/receiver module integration type according on whether a transmitter/receiver module and an antenna are coupled as shown in FIG. 1B.
First, in a transmitter/receiver module separation type roof antenna 1A, an antenna 11 is installed on a roof panel 10, and a transmitter/receiver module 14 is included in a head unit 13 inside a vehicle. The antenna 11 and the transmitter/receiver module 14 are connected to each other through a plurality of RF cables 12 to transmit and receive a signal.
In a transmitter/receiver module integration type roof antenna 1B, an antenna 11 is installed on a roof panel 10, and a transmitter/receiver module 14 is directly connected to the antenna 11 at a lower portion of the roof panel 10. At this time, a module in which the antenna 11 and the transmitter/receiver module 14 are combined is connected to a head unit 13 through an Ethernet cable 17.
Meanwhile, as illustrated in FIG. 2, in the transmitter/receiver module separation type roof antenna 1A, signal attenuation occurs by the plurality of long RF cables 12, and a preamplifier 15 having a higher gain should be installed at the antenna. And in the transmitter/receiver module integration type roof antenna 1B, since the transmitter/receiver module 14 is disposed adjacently, a preamplifier 16 having a relatively low gain is installed at the antenna.
As described above, since the roof antenna has different signal attenuation and impedance according to the above-described transmitter/receiver module separation type and transmitter/receiver module integration type, the antenna should be separately manufactured to have different preamplifiers, and thus an installation process thereof is inconvenient, and also cost of development and maintenance is increased.